ES2278039T3 - TRANSPARENT POLYOLEFINIC FILM, BIAXIALALLY ORIENTED, WITH IMPROVED ADHESION PROPERTIES. - Google Patents

Abstract

The invention relates to the use of a pololyfin film for scaling purposes. The film consists of a base layer which is made of polyolefin polymers and at least one outer covering layer. The covering layer contains at least 50 wt. % of a polyolefin modified by maleic acid anhydride, in relation to the weight of the covering layer, and undergoes flame surface treatment on the surface of said covering layer.

Description

Transparent, oriented polyolefin film biaxially, with improved adhesion properties.

The surface tension of the polyolefin films, using plasma, flame and light discharge. The films are made so printable and wettable with water-based coating systems. While that the light discharge treatment is used for films sealable and non sealable, flame treatment is used Mainly for non-sealable films.

In the flame treatment of the films no sealable, the film is transported on a cold roller, on top of which a gas burner is arranged. The separation between burner and film / roller surface cold so that the oxidation reaction is maximized on the polymeric surface. Oxidized polar groups are formed in the procedure, increasing the surface tension of the film in the desired way.

It is taught to carry out the treatment of non-sealable films at a cold roller temperature greater than 36 ° C (see "The base flame treatment process", H. Angeli / Esse Ci, 3rd International Meeting on the Plastic Surface Treatment, 1989, Narni, Italy). Below this temperature, it produces condensation of water vapor on the surface of movie, making the movie unusable.

In comparison with the discharge treatment luminous, flame treatment of non-sealable films It has advantages. These are a high and constant surface tension In time, little smell of the film and the absence of the effect of back. The disadvantage is the high thermal load on the film surface.

The prior art exposes sealable films. by heat These sealable films generally have layers higher comprising copolymers or terpolymers of propylene, ethylene and / or butylene units. These films are sensitive to thermal load and deteriorate during flame treatment of such that they lose their sensitivity to heat. The use of procedure described above for these sealable films It is therefore not practicable. The thermal load on the surface sealable is too high and a temperature reduction of cold roller results in condensation of water vapor that It has been described.

In the case of sealable films, it is taught therefore to use flame treatment with polarization (see "The polarized flame process", H. Lori / Esse Ci 3rd International Meeting on the Plastic Surface Treatment, 1989, Narni, Italy). In this method, the burner is arranged above the cold roller A direct voltage is applied between the burner and the cold roller, making the ionized atoms of the flame achieve increased acceleration and collide with the surface polymeric with greater kinetic energy. They break more easily chemical bonds within polymer molecules and formation of radical without limits proceeds more quickly. Thermal load on the polymeric surface is smaller than in the case of flame treatment without polarization. At the same temperature of flame, greater surface tension is achieved in the procedure with polarization than in the procedure without polarization. In others words, lower flame temperature is required in order to achieve the same surface tension in the polarized procedure that in the procedure without polarization, resulting in sealing layer protection.

EP 0 732 188 describes a Additional procedure for flame treatment of films sealable In this procedure, the flame is used in the same way without polarization and the film cools considerably on the roller. The temperature of the film surface treated with Call here after leaving cold roll is at most 25 ° C. This procedure has a disadvantage that the temperature program for films and are required Additional cooling devices

The prior art sets forth the procedure for improve the adhesion properties of polyolefin films, in particular polypropylene films. Are treated are you films usually with plasma, flame or light discharge on a or both surfaces during production. These procedures increase the surface tension of the film and improve, by example, its susceptibility to printing and metallization or its adhesion to other coatings.

The disadvantage of these known procedures is that the increased surface tension drops continuously after the movie has been produced. For when it is made the film, the surface tension has dropped frequently so much that an additional treatment of surface before printing, metallization or other steps corresponding processing in order to ensure good desired adhesive strength. With subsequent treatment, without However, the original values are no longer achieved Correspondingly, the adhesion properties of these films or the adhesion properties achieved by these procedures They need improvement.

U.S. Patent 5,346,763 describes a three layer metallizable film. The base layer is HDPE (high density polyethylene). The top layer B is polyethylene modified with maleic acid anhydride (MAH). That layer is metallize The second top layer C is sealable. That second layer Sealable top is formed by non-propylene polymers modified. It will not be mentioned that this sealable layer is subjected to a surface treatment, either by light discharge or by flame. With respect to the upper layer modified with MAH, the example shows describes that surface will be treated with light discharge and that, in addition, a flame treatment can be applied. I dont know expresses that the flame treated MAH modified layer is sealable The MAH modified layer will metallize.

German patent DE 19718192 describes films in which MAH modified polymers are used as adhesion layers. Adhesion layers are between two layers whose adhesion to each other must be improved. In a second In this way, the modified polymer can be mixed with MAH with other polymers and form as a mixture an outer layer. In that case the mixture contains at most 40% of the polymer modified with MAH The use of the top layer with polymer of MAH for sealing, rather that layer should be provided with a metallic layer By tato the treatment by download is foreseen light or flame of polymers modified with MAH, but that Treated layer is not sealed. An additional layer of special sealing untreated counter.

The object of the present invention was therefore so much to provide a polyolefin film that distinguished itself by its particularly good sealing properties. In particular, it is necessary here that the sealable surface can be treated with flame in order to increase the surface tension without undermining the susceptibility of sealing. The film must be economical and cheap to produce. The other service properties required, in particular brightness and turbidity in the case of modalities transparent, the film should not be undermined in the process.

This object is achieved by using a Biaxially oriented polyolefin film for sealing, in which the film comprises a base layer formed with polymers polyolefins and at least one outer top layer, in which This top layer is sealed and comprises at least 50% by weight, based on the weight of the top layer, of modified polyolefin by maleic anhydride and has been treated superficially by means of a flame on the surface of said upper layer.

According to the invention, the film it comprises at least one base layer and one top layer that It forms an outer layer of the film. In general, the top layer to a surface of the base layer. If desired, it you can apply an additional top coat of any desired type to the opposite surface of the base layer. In this way, it get three layer modalities with a top layer treated with flame and sealable. If desired, these modalities can be modified of three layers with additional intermediate layers between the layer of base and upper and outer layers. In this way, it they get four and five layer modalities of the film from according to the invention. All modalities have in common the characteristic that is essential for the invention, that less an upper layer is formed of polyolefin modified with maleic anhydride and has been treated with flame, but continues to be nevertheless sealable.

This top layer of the film comprises generally at least 50% by weight, preferably 80 to 100% by weight, in particular from 95 to <100% by weight, in each case with base in the layer, of polyolefin modified with maleic anhydride, to which is referred to in the following as MAPO. Besides the MAPO, some additional constituents of the top layer may be polyolefin polymers formed with ethylene units, propylene or butylene. These polyolefins are present in a amount of 0 to 50% by weight, preferably 0 to 20% by weight, in particular of> 0 to 5% by weight, in each case based on the layer higher. In order to clearly differentiate from modified polyolefins, reference is made to these non-polyolefins modified, which are present additionally, to the layer superior as a mixing component, hereinafter as polyolefin II. If desired, the top layer further comprises additives conventional in effective amounts in each case.

Polyolefins II are, for example, polyethylenes, polypropylenes, polybutylenes, or copolymers of olefins having 2 to 8 carbon atoms of which They prefer polyethylenes and polypropylenes. Polypropylenes are homopolymers comprising propylene units or copolymers, which also include terpolymers, which are predominantly formed of propylene units; understand generally at least 50% by weight, preferably 70 to 99% by weight, of propylene units, based on copolymer of propylene

In general, the propylene polymer comprises at least 50% by weight, preferably 94 to 100% by weight, of propylene units. The corresponding comonomer content to how much 10% by weight or 0 to 6% by weight respectively consists usually, if present, of ethylene and butylene. The data in percentage by weight they are based in each case on the homopolymer of propylene.

If desired, the polyolefin II used can be isotactic propylene homopolymers having a point of melting from 140 to 170 ° C, preferably 155 to 165 ° C, and an index melt flow (measurement of DIN 53 735 at a load of 21.6 N and 230 ° C) 1.0 to 10 g / 10 min, preferably 1.5 to 6.5 g / 10 min. The soluble n-heptane content of Isothatic propylene homopolymers is generally 1 to 10% in weight, preferably 2-5% by weight, based on The starting polymer.

The polyolefins II used in the layer upper together with the MAPO are preferably copolymers or terpolymers, preferably copolymers of ethylene and propylene or ethylene and butylene, or propylene and butylene or terpolymers of ethylene and propylene and butylene or mixtures of two or more of said copolymers and terpolymers.

In particular, polyolefins II are random ethylene-propylene copolymers that have an ethylene content of 1 to 10% by weight or copolymers randomized propylene-1-butylene which have a butylene content of 2 to 25% by weight, in each case based on the total weight of the copolymer, or random terpolymers from ethylene-propylene-1-butylene which have an ethylene content of 1 to 10% by weight and a content of 1-butylene of 2 to 20% by weight, in each case with based on the total weight of the terpolymer, or a mixture of terpolymers from ethylene-propylene-1-butylene and copolymers of propylene-1-butylene, in which the mixture has an ethylene content of 0.1 to 7% by weight, a propylene content of 50 to 90% by weight and a content of 1-butylene of 10 to 40% by weight, in each case with based on the total weight of the polymer mixture.

The copolymers and / or terpolymers described previously, which are used in the upper layer, they have generally a melt flow rate of 1.5 to 30 g / 10 min, preferably 3 to 15 g / 10 min. The melting point is in the range of 120 to 140 ° C. The mixture described above of copolymers and terpolymers have a melt flow rate 5 to 9 g / min and a melting point of 120 to 150 ° C. All the melt flow rates indicated above are measured at 230 ° C and a force of 21.6 N (DIN 53 735).

The molecular weight distribution of polyolefins II described above may vary in limits wide depending on the area of application. The relationship between the weight average molecular weight M w and the average molecular weight in number M_n is generally between 1 and 15, preferably in the range from 2 to 10. The molecular weight distribution is achieved of this type, for example, by degradation with peroxide or by preparing the polyolefin by means of catalysts Suitable metallocene.

Polyolefins modified with anhydride Maleic are polyolefins that have been hydrophilized by incorporation of maleic acid units. These polyolefins modified are known per se in the prior art and are also known as technically produced polymers. It takes carry out the modification by reacting the polyolefins with maleic anhydride by suitable manufacturing steps. Be they also know these procedures in the art previous.

The base polyolefins used for the reaction with maleic anhydride the polyolefins II can be in principle described above, in that, for the purposes of this invention, propylene homopolymers or copolymers of propylene or predominantly formed propylene terpolymers of propylene units generally comprising at least 50% by weight preferably 70 to 99% by weight, of units of propylene, based on the propylene copolymer, as polymers of basis for modification. The preparation of these polypropylenes modified with maleic anhydride are known per se in the art above and are described, for example, in the U.S. Pat. 3,433,777 and the U.S. Pat. 4,198,327.

The density, according to ASTM D 1505, of the modified polyolefins, preferably propylene polymers modified, it is preferably in the range of 0.89 to 0.92 g / cm3, is in particular 0.9 g / cm3, the point of Vicat softening according to ASTM 1525 is in the range from 120 to 150 ° C, in particular from 140 to 145 ° C, the Shore hardness of according to ASTM 2240 is 55 to 70, preferably 77 ° C, and the melting point according to ASTM D 2117 is in the range of 140 to 165 ° C, preferably 150 to 165 ° C, in particular 155 to 160 ° C the content of maleic acid in the modified polyolefin, preferably propylene polymer, is generally less than 5%, based on the modified polyolefin, is preferably in the range of 0.05 to 3%, in particular 0.1 to 1%. The index of melt flow of the modified polyolefin, preferably polypropylene, is generally 1 to 20 g / 10 min, preferably from 3 to 10 g / 10 min.

The following are preferably used propylene polymers for anhydride modification maleic:

Isotactic propylene homopolymers are used having a melting point of 140 to 170 ° C, preferably 155 at 165 ° C, and a melt flow rate (measurement DIN 53 735 a a load of 21.6 N and 230 ° C) from 1.0 to 10 g / 10 min, preferably 1.5 to 6.5 g / 10 min. The soluble content in N-heptane of propylene homopolymers isotactic is generally 1 to 10% by weight, preferably of 2-5% by weight, based on the polymer of departure.

Copolymers of ethylene and propylene or propylene and butylene or terpolymers of ethylene and propylene and butylene or mixtures of two or more of said copolymers and terpolymers.

Particular preference is given to random ethylene-propylene copolymers that have an ethylene content of 1 to 10% by weight or at random copolymers of propylene-1-butylene which have a butylene content of 2 to 25% by weight, in each case based on the total weight of the copolymer, or random terpolymers of ethylene-propylene-1-butylene which have an ethylene content of 1 to 10% by weight and a content of 1-butylene of 2 to 20% by weight, in each case with based on the total weight of the terpolymer, or a mixture of terpolymers from ethylene-propylene-1-butylene and copolymers of propylene-1-butylene, in which the mixture has an ethylene content of 0.1 to 7% by weight, a propylene content of 50 to 90% by weight and a content of 1-butylene of 10 to 40% by weight, in each case with based on the total weight of the polymer mixture.

The copolymers and / or terpolymers described previously, which are used for modification, they have generally a melt flow rate of 1.5 to 30 g / 10 min, preferably 3 to 15 g / 10 min. The melting point is at range from 120 to 140 ° C. The mixture described above of copolymers and terpolymers have a melt flow rate 5 to 9 g / 10 min and a melting point of 120 to 150 ° C. All the melt flow rates indicated above are measured at 230 ° C and a force of 21.6 N (DIN 53 735).

The top layer can comprise additionally, if desired, conventional additives, such as neutralizers, stabilizers, antistatic agents anti-blockers and / or lubricants, in effective amounts in each case.

It has been found that the surface of the layer superior is extremely suitable for surface treatment by middle of a flame. The values obtained for the tension superficial are high, preferably in the range of 37 to 50 mN / m, in particular from 39 to 45 mN / m. Surprisingly, the movie it still has excellent sealing properties even after of the corresponding flame treatment and can be used for both according to the invention for the production of packing heat sealed and surface treated. This is particularly noteworthy in view of the adverse effect of flame treatment in the susceptibility of sealing that is described in the prior art. The conventional materials of top layer that have not been modified with maleic anhydride lose its sealing properties virtually completely after flame treatment

In addition, the use of flame treatment prevents impairment of processing properties through the effects from the back on the opposite surface. Adverse effects are known. of that type, for example, for the treatment with light discharge of the sealable films. As a result, the movie exhibits, due to flame treatment, good adhesion to the inks of printing, excellent sealing properties and the absence of reverse effects. The sealing resistance that is achieved they are between 0.7 and 2.5 N / 15 mm (HST 130 ° C, 10 N / cm2, 0.5 s). Surprisingly, the resistance to sealing after flame treatment is in the same order of magnitude as after of the light discharge treatment, that is, the sealing by flame treatment.

The base layer of the polyolefin film It is basically formed with the polyolefins II described above, of which preference is given to homopolymers of propylene described, in particular propylene homopolymers isotactic In general, the base layer comprises at least 70 to 100, preferably 80 to <100% by weight, of polyolefin or propylene polymer In addition, the base layer usually comprises neutralizers and stabilizers, if desired, additives additional conventional in effective amounts in each case. For opaque or white-opaque modalities of the film, the base layer additionally comprises pigments and / or Vacuum initiator fillers. The type and quantity of Fillers are known in the art.

The thickness of the top layer comprising modified polyolefin is greater than 0.1 µm and is preferably in the range of 0.3 to 3 µm, in particular of 0.4 to 1.5 µm.

If desired, the film may have layers additional, preferably a second upper layer and, if you want, intermediate layers on one or both sides.

The intermediate layers may consist of polyolefins II described and, if desired, comprise additives conventional, such as antistatic, neutralizers, lubricants and / or stabilizers and, if desired, agents anti-blockers The thickness of the intermediate layers, if they are present, is greater than 0.3 µm and is approximately in the range from 1.0 to 15 µm, in particular from 1.5 to 10 µm.

The second upper layer may be formed also of the polyolefins II described. The modalities Sealable and non-sealable are therefore possible for the second top layer. If desired, the top layer comprises additives conventional methods similar to that of the other layers. Thickness of this second top layer is 0.5 µm to 5 µm, preferably 0.5 to 2.5 µm.

In an additional mode, the second layer upper can be formed, like the first top layer with modified polyolefins and, if desired, flame treated if You want to increase surface tension.

The total thickness of the polyolefin film of according to the invention may vary within wide limits and It depends on the intended use. It is preferably 4 to 100 µm, in in particular from 5 to 80 µm, preferably from 10 to 50 µm, constituting the base layer of 40 to 98% of the total thickness of the movie.

The invention further relates to a procedure for the production of the polyolefin film of according to the invention by the coextrusion process, which is known in itself.

This procedure is carried out, coextruding the melts corresponding to the individual layers of the film through the flat film stamp, removing the resulting film on one or more rollers for solidification, subsequently extending (orienting) the film, dealing with heat the extended film and, if desired, dealing with discharge luminous or with flame the surface layer destined for the treatment.

Extension is carried out (orientation) biaxial sequentially or simultaneously. The sequential extension usually consecutively, preferring the consecutive biaxial extension in which it leads to out first in longitudinal direction (in the direction of the machine) and then transverse (perpendicularly the direction of the machine). Simultaneous extension can be carried out. by the procedure for flat films or by the blowing procedure It describes in more detail the film production, using the extrusion example of flat films with subsequent sequential extension.

First, as usual in the Extrusion process, the polymer or the mixture of polymers of the individual layers and liquefied in an extruder, being possible that some added additives are already present optionally in the polymer or polymer blend. Are made pass simultaneously the melts in a stamp (prints of slot) for flat films and the extruded film is removed from multiple layers on one or more removal rollers, during which It cools and solidifies.

The film obtained in this way extends then longitudinally and transversely to the extrusion direction, which results in the alignment of the molecular chains. The longitudinal extension is advantageously carried out with the support of two rollers at different speeds corresponding to the target extension relationship and extension is carried out transversal advantageously with the help of the appropriate tension frame. The ratio of this longitudinal extension is in the range of 4 to 8, preferably 5 to 6. Extension ratios transverse are in the range of 5 to 10, preferably 7 to 9.

The extension of the film is followed by the thermofragment (heat treatment) thereof, in which maintains the temperature of 100 to 160 ° C for approximately 0.1 to 10 seconds. The film is subsequently rolled up so conventional by means of a winding device.

It has turned out to be particularly favorable keep the roller or removal rollers, whereby the extruded film is cooled and solidified at a temperature of 10 at 160 ° C, preferably from 20 to 50 ° C, by means of a circuit of heating and cooling.

The temperatures at which the longitudinal and transverse extension may vary in an interval relatively broad and depend on the desired properties of the movie. In general, longitudinal extension is carried out preferably at 80 and up to 150 ° C and extension is carried out preferably at 120 and up to 170 ° C.

After biaxial extension, it is treated with called the top layer comprising modified polyolefin, of according to the invention by the method known per se. Be describe flame treatment procedures, for example, in EP 0732 188. The intensity of the treatment is generally in the range of 37 to 50 mN / m, preferably 39 at 45 mN / m. In general, this flame treatment is carried out by middle of a flame without polarization. If desired, it is also possible Use polarized flames. During the flame treatment, it passes the film on a cold roller, with a Burner above this roller. This burner is installed generally at a distance of 3 to 10 mm from the surface of cold film / roller. During contact with the flame, the Film surface undergoes an oxidation reaction. Be cool the film preferably through the cold roller for the treatment. The temperature of the roller is in the range of 15 to 65 ° C, preferably 20 to 50 ° C.

The invention is now explained with reference to An example guide:

Example 1

A transparent film of three was produced layers consisting of a base layer B, a top first base A and a second upper base C with a total thickness of 30 µm per coextrusion, followed by step-by-step orientation in longitudinal and transverse directions. The first top layer A it had a thickness of 1.0 µm and the second top layer C had a 0.7 µm thickness. The layers had the following compositions:

C base layer

99.64% in weight  \ begin {minipage} [t] {120mm} of homopolymer of propylene having a melting point of 165 ° C and an index of 3.4 g / 10 min melt flow and an isotacticity index 94% chain; \ end {minipage} 0.10% in weight of Erucamide (lubricant); 0.10% in weight from Armostat 300 (antistatic); 0.03% in weigh of neutralizer (CaCO3); 0.13% in weight of stabilizer (Irganox).

Top layer A

100% in weight  \ begin {minipage} [t] {120mm} of polypropylene modified by maleic anhydride having an acid content 0.1% maleic by weight, based on the polymer; \ end {minipage}

Top layer C

99.54% in weight  \ begin {minipage} [t] {120mm} of random copolymer which comprised ethylene and propylene that had a flow rate of melt of 6.0 g / 10 min and an ethylene content of 6% by weight, based on the copolymer; \ end {minipage} 0.22% by weight from SiO_ {2} as an anti-blocking agent that had an average size of 4 µm particle; 0.20% by weight from stabilizer (Irganox 1010 / Irgafos 168); 0.04% in weight of neutralizer (Ca stearate).

The production conditions in the steps Procedure individuals were as follows:

Extrusion: Temperatures: Layer of base B: 270 ° C Cap higher TO: 250ºC Cap higher C: 270 ° C Temperature roller of retirement: 30ºC Extension longitudinal: Temperature: 100ºC Relationship of extension longitudinal: 1: 4.5 Extension cross: Temperature: 170 ° C Relationship of extension cross: 1: 9 Setting: Temperature: 140ºC Convergence: 10%

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The surface of upper layer A was treated by middle of a flame that had a flame temperature of approximately 690 ° C. This flame was produced, burning a mixture of air / natural gas with a flow rate of 120 m 3 / h.

The transverse extension ratio of 1: 9 is An effective value. This effective value is calculated from the width film end B reduced by twice the seam width b, divided by the width of the extended C film longitudinally, also reduced by twice the width of sewing b.

Immediately after treatment with called, the film had a surface tension of 44 mN / m on the surface of the top layer A. With subsequent printing, the Film exhibited very good adhesion of printing ink. It was possible to heat seal the film under HST conditions (sealing temperature 130 ° C; sealing pressure 10 N / cm2, contact time 0.5 s). The sealing resistance of a A / C sealing seam was 2.0 N / 15 mm.

Comparative example one

A movie was produced as described in the Example 1. In contrast to Example 1, it was treated superficially the upper layer A by means of a light discharge. The movie It also had good sealing properties. However, the film exhibits transparent reverse effects on the surface opposite, resulting in blockage during winding and optical defects with surface printing A.

Comparative example 2

A movie was produced as described in the Example 1. In contrast to Example 1, it was used in the layer superior to an unmodified polypropylene copolymer that had a ethylene content of about 5% by weight. This movie exhibited very good sealing properties without treatment with call. After flame treatment, resistance to sealing under identical sealing conditions was only 0.8 N / 15 mm

The following measurement methods were used To characterize the starting materials and films:

Melt Flow Rate

The melt flow rate of conforming to DIN 53 735 at a load of 21.6 N and 230 ° C.

Melting point

DSC measurement, maximum melting curve, heating rate 20 ° C / min.

Surface tension

The surface tension was determined by called ink method (DIN 53 364).

Print susceptibility

The treated films were printed previously. Adhesion of the ink was assessed by means of Test with adhesive tape. If little ink was removed by means of a adhesive tape, the adhesion of the ink was assessed as moderate and if an insignificant amount of ink was removed, it was valued as deficient.

Sealing resistance

In order to determine the resistance to sealing, two films are laid on top of each other with their sides modified and heat sealed at a temperature of 130 ° C and a sealing time of 0.5 s and a sealing pressure of 10 N / cm2 in a Brugger HSG / ETK heat sealing unit. Be cut test strips with a width of 15 mm of the samples heat sealed. The two strips are subsequently released to 200 mm / min Using the T detachment method in a machine tension tests, with a sealing seam plane that forms a right angle to the tension direction. Resistance to heat sealing quoted is the force necessary to separate the test strips.

Claims (11)

1. The use of a polyolefin film coextruded, biaxially oriented, for sealing, in which the film comprises a base layer formed with polymers polyolefins and at least one outer top layer, in which This top layer comprises at least 50% by weight, based on the weight of the top layer, of a polyolefin modified by maleic anhydride and has been treated superficially by means of a flame on the surface of said upper layer. 2. The use as claimed in the claim 1, in which the content of maleic acid in the modified polyolefin is in the range of 0.05 to 5% by weight, based on the modified polyolefin. 3. The use as claimed in claim 1 or 2, in which the modified polyolefin has a melting point, of according to DSC, in the range of 140 to 165 ° C. 4. Use as claimed in any of the claims 1 to 3, wherein the base polyolefin used for the modification is a propylene homopolymer or a copolymer of propylene-ethylene or a terpolymer of propylene-ethylene-butylene. 5. The use as claimed in the claim 4, in which the propylene-ethylene copolymer as base polyolefin has an ethylene content in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight. 6. Use as claimed in any of the claims 1 to 5, wherein the top layer comprising Modified polyolefin is in the range of 0.3 to 3 µm. 7. Use as claimed in any of the claims 1 to 6, wherein the top layer comprising modified polyolefin further comprises a non-polyolefin modified, preferably a propylene homopolymer, a propylene-ethylene copolymer or a terpolymer of propylene-ethylene-butylene. 8. Use as claimed in any of the claims 1 to 7, wherein the resistance to sealing by Heat is in the range of 1.0 to 2.0 N / 15 mm. 9. Use as claimed in any of the claims 1 to 8, wherein the surface tension after Flame treatment is in the range of 39 to 50 mN / m. 10. Use as claimed in any of the claims 1 to 8, wherein the film has a second layer higher. 11. The use as claimed in the claim 10, in which the film additionally has an intermediate layer in one or both sides.